


Biological Specificity

by OneOfThoseThings



Series: Interspecies Compatibility [1]
Category: Doctor Who (2005)
Genre: Alien Biology, Alien Cultural Differences, Alien Gender/Sexuality, Can be read as platonic but I personally ship TF out of these two, Cotton Candy Fluff, Gen, Humor, Interspecies Awkwardness, Post-Episode: s04e06 The Doctor's Daughter, Time Lords Are Aliens, no beta we die like men
Language: English
Status: Completed
Published: 2020-02-17
Updated: 2020-02-17
Packaged: 2021-02-28 05:55:14
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,027
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22779055
Author URL: https://archiveofourown.org/users/OneOfThoseThings/pseuds/OneOfThoseThings
Summary: Donna gets curious. The Doctor puts up with it. A detailed lesson in Time Lord biology and culture ensues.
Relationships: Tenth Doctor & Donna Noble
Series: Interspecies Compatibility [1]
Series URL: https://archiveofourown.org/series/1637608
Comments: 26
Kudos: 176





	Biological Specificity

**Author's Note:**

> Biological Specificity (aka Wikipedia): The tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species.

The entire time Martha was on board, Donna kept loudly announcing how nice it was to have another human woman to talk to. The Doctor pointed out that he already had one of those and he found it to be a mixed bag at best. He remembered Martha being a lot quieter. He suspected Donna was a bad influence on everyone. 

After dropping Martha off, their latest exploit ended in a lovely celebration with some sort of nectar that seemed to be having a calming, if slightly inebriating effect on his companion. She leaned into his space, slinging an arm over his shoulders as they made their way back to the TARDIS. 

She was staring, again. She’d been staring a lot recently. He kept meaning to bring it up. Now seemed like as good a time as any. “Why are you looking at me like that?” 

He expected her to argue or get defensive― her two primary settings seemed to be anger or indignation― but she just blinked, looking strangely thoughtful. She opened her mouth and then closed it, looking away. 

“What?” he asked.

She gave him a quick look out of the corner of her eye. “Nothing.”

“What is it?” he asked, unbearably curious about what could possibly put Donna Noble off asking anything. 

“It’s rude,” she mumbled into her glass. 

He laughed a little at the idea that Donna considered herself in any way restrained from being rude, and then laughed louder at her indignant face. “I’m sorry, are you implying that the level of rude you are currently is not the maximum possible level of rudeness available?”

“Oi, you’re one to talk!”

“Donnn-naaa,” he wheedled, “What is it?”

Donna sipped her nectar, flicking glances at him out of the corner of her eye. “Do your lot― How do you… reproduce?” she grimaced a little on the last word.

“That’s not even the rudest question you’ve come up with _today!”_ he scoffed. “Time Lords are loomed.” 

Donna’s eyebrows shot up and then scrunched back down. “Loomed?” she repeated. “Like a poncho?” 

He laughed. “No― Do I look like a poncho to you? Genetic looms, obviously.” 

“Oh, obviously,” she mocked.

“You did ask,” he reminded her, and she miraculously snapped her mouth shut. Purely for the sake of positive reinforcement, he decided to continue. “It’s all very scientific. Each family has its own loom. Genetic material goes in, Gallifreyans come out.” 

“Right,” she said, very slowly. “Bog standard genetic loom experience, then.” 

He grinned, patting her on the head. “Exactly. Now what would you say to some toast? All that hot air ballooning really made me crave toast.” 

She didn’t seem to register any of that. “If you use looms to reproduce, does that mean you’re asexual?” 

“More or less,” he said. “Were you planning on one of us seducing the toast?” 

Donna blinked at him. “What?” 

He decided to speak very slowly. “I’m going to make toast. If you try very hard not to have sex with it, I’ll answer your questions.”

Donna screwed up her face, clearly torn between arguing― her natural state― and getting to ask further questions. She opened her mouth and closed it, visibly fighting her instincts. With a strangely stilted air of formality, she gestured toward the galley. 

He patted her head and walked on. “Now then, what is it you’d like to know?” 

He could practically hear Donna’s thoughts whirring. “So you never have sex?” 

“I am physically capable of having intercourse.”

“ _Have_ you had it?”

He considered. “Probably.” 

Donna scoffed, “What do you mean _probably_? It’s sort of a yes or no question.”

“Well, it depends on what you mean.”

“What do you _mean_ what do I mean?” Her voice jumped up an octave. “I mean―“ Something visibly occurred to her. “Wait. What do _you_ mean? Is your version different? Do you even know what _I_ mean?” 

He frowned. “Have you been working your way up to ask for an anatomy lesson?”

“No!” she said, then reconsidered, “...maybe. You know what, probably― yes! Let’s start with the anatomy. How different is it from humans. Do you actually know human anatomy or do you want me to draw you a picture?”

The Doctor had seen Donna attempt to draw a horse once. He shuddered to think what she’d make of an anatomical diagram. “Donna, for the last time, I might not have a degree from Cambridge, but I am, in fact, a doctor.” 

“You don’t have _any_ degree! You’re basically a skinny alien version of that guy from ‘Catch Me If You Can!’ No― Never mind. No time for that!” she cut herself off. “Fine. So based on your encyclopedic knowledge of human anatomy, how closely do Time Lords match up?” 

He considered. “60% overall, 75% for reproductive systems, 90% for genitalia. Give or take.” 

Donna blinked at him. “You what?”

“I have two hearts and a respiratory bypass. Would you consider that relevant to your current line of inquiry?” he clarified.

She darted a glance down to his chest and then immediately wrenched her eyes back up to his face. “Guess not. Fine― What’s the 25%? What’s the 10%? Wait, are we talking 10% in one category plus 15% when you add more bits or are we talking 10% and then a whole separate 25% on top of that?” 

The Doctor, having some experience with Donna’s bizarre leaps in logic, still found himself more than a little hard-pressed to follow whatever that was. “I don’t― Forget the percentages. Maybe it’d be easier for me to just explain.” 

Donna nodded, perching herself by the counter like he’d just promised to tell her a grand fairytale.

He resisted the urge to just make something up for the flourish. “Right. So. Time Lords, like most long-lived species, aren’t driven by a constant need to reproduce. If we went at it as often as you lot we’d have overpopulated within a single generation. So we evolved away from all that eons ago.” 

“So you can’t shag?” Donna interrupted.

“'Can’t' is a strong word. More like 'don’t.'”

Donna propped her chin up in her hands, looking more attentive than she ever had under any other circumstances. Classic human. If they weren’t actively reproducing, they were just hoping someone else would bring it up.

“There’s a mental component,” he continued, resisting the urge to tease her about her very human level of interest. “That’s most of the difference, realistically. Touch telepaths, you know.” 

Donna nodded. “Like the Ood.” 

He couldn’t quite help pulling a face at the suggestion. “No, the Ood are a hive mind. They’re always linked. Sort of an open network, if you will. Touch telepaths choose our connections…more carefully.”

Donna nodded along. He suspected she was just waiting for him to get back to the sex bit. But she was at least feigning interest.

“Instead of being driven by a desire to breed, we have more of a drive to connect.” He didn’t add any judgments on how risky it seemed to be to let hormones dictate your every move, by contrast. 

Donna stopped nodding, looking a bit sick. “Hang on, did you get off on mentally chatting up those Ood? Were you having mind sex that whole time?? You could have at least stopped holding my hand!!”

“What? No! _What?!_ ” the Doctor sputtered, “Of course not! And it’s not called ‘mind sex’― where do you get your ideas??” 

“You just said―“

“It’s called telepathic synthesis, if you must know. And obviously I didn’t have it with the Ood. It only works between Time Lords!” 

Donna breathed an exaggerated sigh of relief and then held up her hands placatingly. “Not that I’d judge you!” 

“No, you seem very neutral on the subject.” He rolled his eyes. 

Her expression suddenly darkened. “Hang on― You can only bond with other Time Lords? But you said you’re the last one!” She looked increasingly horrified as the implications set in. 

Trust Donna to immediately spot and put her finger right on that wound. 

“Right, but that’s not exactly the sort of thing biology tends to plan for,” he said. “Bit of a miss, from that perspective.” He shrugged philosophically. 

Donna seemed to find his calm response even more upsetting somehow. “But that’s terrible!” She jumped up from her post at the counter and snatched him into a bracing hug. “I’m so sorry,” she mumbled into his collar, gripping him as hard as her human hands could manage. 

“Ah well,” he sighed and patted her hair, “Best not to dwell.” 

She gripped him tighter, like a vice. “I don’t want you to be all on your own,” she mumbled into his jacket. 

“That’s sort of a funny thing to say while hugging someone, isn’t it?” 

* * *

More than any of his previous companions, Donna seemed to fixate on strange details, turning them over in her mind for days and days. They’d have a random interaction once and then days later, without any prompting, she’d suddenly jump back in to a conversation mid-stream. 

The Doctor had been told on more than one occasion that his own thought processes were a bit scattered from the outside. Donna Noble’s chaotic jumble of randomly connected shards of concepts made his leaps of logic seem like a carefully curated curriculum by comparison.

“How do you know you can’t form telepathic links with anyone but Time Lords?” she asked one day, like they hadn’t been in the middle of a conversation about arthropod migration patterns. 

“What?” he asked, trying to decide which part of that could have possibly connected to the topic at hand. 

“You said you can only bond with other Time Lords,” she said, like he was a bit slow for not remembering. “How do you know? Have you tried it with anyone else?”

The Doctor couldn’t help but pull a face at the suggestion. “That’s a bit like me asking how you know you can’t have sex with dolphins. Do you need to _try_ having sex with dolphins to rule that out?”

Donna looked distinctly put off, but forged ahead. “Listen, I’m not saying it’d be Plan A or even Plan B, but if I knew for a fact that I was the only human left and I was going to have to hang around with a bunch of dolphins for the rest of my life, if one offered to try it I might be willing to at least consider it.” 

The Doctor spared a thought for Jack, whom he might have judged unfairly before collecting a large enough sample size of humans to compare against. 

To Donna, he said, “I think we might want to put off the trip to the diamond coral reefs of Kataa Flo Ko for a bit while you work through whatever it is you’re working through.” 

Donna flapped her hands around exasperatedly. “I’m not talking about me, dumbo! I’m talking about you!” 

“Right…” he said slowly, “To be clear, I _definitely_ don’t want to have sex with dolphins.” 

“Forget the dolphins!” Donna shouted. “We’re not talking about flipping dolphins! I’m talking about your mind meld thing! Have you ever tried to do it with anyone who wasn’t a Time Lord?” 

He didn’t even try to disguise his revulsion. “Of course not!” 

“Well, why don’t you give it a go?” she asked, blunt as ever.

“I’m having trouble coming up with an analogy that doesn’t reference bestiality here.” 

Donna waved that off. “I’ll just come right out with it then― Would you like to try doing that mind meld thing with me? I’m offering.” She raised an authoritative finger. “Do not call me any kind of wild animal in the next sentence!” 

The Doctor honestly didn’t know what to do with that. His brain whirred, flipping frantically through all possible scenarios and outcomes and coming up with exactly nothing useful for this completely unforeseen turn of events. 

Donna stared at him, hard, for another 39 seconds and then, just as suddenly, backed off. 

“Just think about it,” she said. “Offer’s open.” She gave him a long, pointed look, and then ―impossibly― just shook all of that off and went back to talking about arthropods. 

**Author's Note:**

> I’m also on [tumblr](https://1-of-those-things.tumblr.com/).


End file.
